초록 ▼

A metal mold to be used for injection-molding of a flat plastic disc. The flat, annular mold cavity has a substantially continuously increasing axial thickness away from the injection gate. The gate can be in the center or on the outer periphery of the mold. A split mold type is disclosed wherein at

A metal mold to be used for injection-molding of a flat plastic disc. The flat, annular mold cavity has a substantially continuously increasing axial thickness away from the injection gate. The gate can be in the center or on the outer periphery of the mold. A split mold type is disclosed wherein at least one of the inner opposed surfaces tapers away from an imaginary flat center plane. Alternatively, a stamper having a tapering thickness can be used in a mold having parallel opposed inner surfaces.

대표청구항 ▼

In a metal mold to be used for injection-molding a flat plastic disc having uniform thickness for a high-density information recording carrier by injecting molten resin into a flat and annular mold cavity, the improvement characterized in that an axial thickness of the flat and annular injection mol

In a metal mold to be used for injection-molding a flat plastic disc having uniform thickness for a high-density information recording carrier by injecting molten resin into a flat and annular mold cavity, the improvement characterized in that an axial thickness of the flat and annular injection mold cavity is substantially continuously increased away from a gate at the center of the molding cavity outwardly from the gate to the mold cavity perimeter for injecting the molten resin into the center of the mold and forming a flat resin disc having uniform thickness when molten resin is injection molded in said cavity.